CVE-2026-97741 in Excel
Summary
by MITRE • 10/15/2026
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Excel application, specifically manifesting as a heap-based buffer overflow. This type of memory corruption error occurs when a program writes data beyond the allocated boundaries of a buffer located in the heap segment of computer memory. In the context of Excel, this typically involves the processing of complex or malformed spreadsheet files that contain specially crafted objects, formulas, or embedded elements designed to exploit specific parsing routines within the application's engine. The attacker crafts input data that exceeds the expected size limits defined by the software for a particular buffer allocation. When Excel attempts to process this oversized payload during file opening or rendering operations, it fails to perform adequate bounds checking, resulting in adjacent memory being overwritten with arbitrary data.
The operational impact of this vulnerability is severe due to its potential for remote code execution over a network. An attacker can host the maliciously crafted Excel file on a web server and trick a user into accessing it via a link or by downloading it from an untrusted source. Upon opening the file, the exploit triggers the heap overflow condition within the application's memory space. Because modern operating systems employ various mitigations such as Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR), successful exploitation often requires chaining multiple vulnerabilities to bypass these protections or relies on specific configurations where mitigation is disabled. If successfully exploited, an attacker gains the ability to execute arbitrary code with the same privileges as the current user. This can lead to complete system compromise, including data theft, installation of malware, and lateral movement within a corporate network if the affected machine serves as a gateway for further attacks.
From a classification perspective, this vulnerability aligns with Common Weakness Enumeration (CWE) ID 120, which defines buffer copy without checking size limits, specifically in the context of heap memory allocation. The attack vector is categorized under CWE-78 or related injection flaws depending on how the payload is delivered and executed within the application environment. In terms of adversary tactics, this scenario maps to MITRE ATT&CK technique T1205.008, which describes Supply Chain Compromise via trusted software updates or distributions, although more directly it fits into Initial Access techniques such as T1566.001 (Phishing: Spearphishing Attachment) where the malicious Excel file serves as the delivery mechanism for initial compromise. The exploitation relies on social engineering to induce the victim to open the document, making user awareness a critical component of defense alongside technical controls.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. Microsoft has likely released security updates or patches that correct the memory handling logic within Excel to enforce strict bounds checking before writing data to heap buffers. Organizations should prioritize applying these cumulative security updates across all endpoints running vulnerable versions of Office Excel. Additionally, implementing application control policies such as AppLocker or Windows Defender Application Control can prevent unauthorized scripts from executing after exploitation occurs. Network segmentation and firewall rules restricting access to untrusted web content reduce the likelihood of users encountering malicious files hosted on external servers. Furthermore, enabling Protected View for documents originating from the internet forces Excel to open these files in a sandboxed environment with limited permissions, thereby containing any potential exploit attempts within an isolated context that cannot affect the host system or network resources.